In general, an eco-friendly vehicle such as an electric vehicle (EV) or a plug-in hybrid electric vehicle (PHEV), which uses an electric motor as a drive source for driving the vehicle, has a high-voltage battery for supplying electricity to the motor. The high-voltage battery is rapidly charged through a rapid charger or charged by being connected to a general external AC power source through an on-board charger (OBC) mounted in the vehicle.
If external AC power is applied to the vehicle, the OBC converts the AC power into rechargeable DC power, thereby charging the high-voltage battery.
FIG. 1 is a schematic view showing a configuration of an OBC of an eco-friendly vehicle. FIG. 2 is a graph showing an AC voltage and an AC current for illustrating an initial operation of the OBC.
As shown in FIG. 1, an OBC 3 includes an input filter 4, a power connector 5, a rectifier 6, a power factor corrector circuit (PFC) 7, and a DC/DC converter 8. These components are controlled through a controller (not shown) mounted in the vehicle.
The power connector 5 is provided between the input filter 4 connected to external AC power 1 to filter and eliminate noise of the AC power 1 and the rectifier 6 for rectifying AC power, thereby reducing an inrush current instantaneously flowing when the AC power 1 in which noise is eliminated is applied from the input filter 4 and reducing voltage loss after the AC power is connected.
Specifically, the power connector 5 includes a resistance element for reducing an inrush current (a phenomenon in which a large amount of current instantaneously flows when AC power is first applied) flowing at a point of time when the AC power 1 is applied to protect internal elements of the OBC 3, and a relay for reducing voltage loss after the AC power 1 is connected to the OBC.
An initial operation of the OBC 3 including the power connector 5 will be described with reference to FIG. 2. If the AC power 1 is applied to an input terminal of the OBC 3, an inrush current instantaneously introduced with a large value is generated while a current for charging a capacitor inside the OBC 3 is introduced at a point of time when the AC power is applied. The current introduced into the OBC 3 flows through the resistance element of the power connector 5, and the relay is connected after the capacitor is sufficiently charged (charged within a few ms). After the relay is connected as described above, the charging of a high-voltage battery 2 is started.
As known in the art, the PFC 7 performs power factor correction, and the DC/DC converter 8 boosts an output voltage of the PFC 7 to a DC voltage for charging the high-voltage battery 2.
However, as the power connector 5 of the OBC 3 includes the resistance element through which an initial charging current including the inrush current flows before the charging of the high-voltage battery 2 starts, and the relay through which a current not including the inrush current flows by the relay being connected when the charging of the high-voltage battery 2 starts, the volume of the OBC increases, and therefore, it is inadequate to increase the output density of the OBC, which is disadvantageous in packaging.
Since the efficiency of the OBC and the fuel efficiency of the eco-friendly vehicle have a relationship of one to one (the fuel efficiency is increased by 1% when the efficiency is increased by 1%), it is required to maximize the efficiency of the OBC. However, the efficiency of the OBC is reduced due to excessive power consumed in operating a mechanical relay and efficiency reduced by contact resistance when the relay is connected.
Since the relay of the power connector 5 is weak against heat dissipation, additional components (e.g., a thermal pad, a heat pipe, etc.) are required to prevent an increase in temperature, and therefore, an increase in cost is caused.